1. Field of the Invention
The present invention relates to a collision sensing system for a side air bag system for detecting a collision of another vehicle against the side of a vehicle to inflate an air bag for protecting an occupant from a secondary collision.
2. Description of the Related Art
An air bag system for inflating its component air bag at the time of a collision against the side of a vehicle thereby to protect an occupant inflates the air bag with the inert gas such as nitrogen gas which is produced by an inflater. Especially in the air bag system of electric type, a gas producing agent in the inflater is ignited in response to a signal which is output from a collision sensor such as a pressure sensitive sensor or a contact sensor arranged in a predetermined position of the vehicle body when the collision sensor detects the collision. Then, the air bag is instantly charged to inflate with the massive gas produced by the inflater. As a result, the air bag is expanded between a vehicle occupant and the inner side wall of the compartment such as the inner wall of the side wall thereby to protect the occupant from any secondary collision against the inner side wall of the compartment.
Collision sensing systems for the side air bag system of the aforementioned kind have already been proposed by us and others as in Japanese Patent Publication No. 5-69791. FIGS. 8 and 9 show one example of the collision sensing system, FIG. 8 is a block diagram showing the collision sensing system, and FIG. 9 is a layout showing the arrangement of sensors. This collision sensing system is equipped in the individual side doors at the two sides of a vehicle body 1 with contact type side collision sensors 2, which are disposed fully of the door width, and on the side doors at the inner sides of the compartment with air bag modules 3, each of which is equipped with a not-shown air bag and an inflater for inflating the air bag. And, the side collision sensor 2 at each side door sends an ignition signal to the corresponding inflater when it detects a side collision. At the vehicle body 1, on the other hand, there are disposed acceleration sensors 4 and an air bag actuation control unit 5. If one of the acceleration sensors 4 detects an acceleration higher than a predetermined level, the air bag actuation control unit 5 sends an ignition signal to the corresponding inflater.
If, moreover, one of the collision sensors 2 and/or one of the acceleration sensors 4 detect a side collision, the air bag disposed in a position necessary for protecting the corresponding occupant is inflated.
In the collision sensing system for the side air bag system thus far described, however, the air bag may possibly be expanded in the following cases even at the time of non-collision, in which the air bag need not be operated. Specifically, in case the side door is violently opened with the vehicle being halted, in case the side door hits an obstacle such as a pole of street lighting, in case the open side door is hit by another automobile or a bicycle, or in case the side door is violently shut, either the collision sensors 2 disposed in the side doors or the acceleration sensors 4 disposed at the vehicle body may be turned ON by an impact similar to that at the time of a side collision thereby to send the ignition signal to the corresponding inflaters.